Study area
Samples of seaweeds were collected seasonally between autumn 2012 and summer 2013 from the intertidal zone of Safaga (26o46ʹN, 33o56ʹE), Hurghada (27o12ʹN, 33o50ʹE) and Al-Quseir (26o5ʹN, 34o17ʹE) along the coast of the Red Sea, Egypt.
Water analysis
Surface water samples were collected seasonally, from the same areas and during the same time of sampling of macroalgae and all variables were measured in triplicate for each sample. Water temperature was measured in situ. Before analysis of seawater, the samples were filtered through Whatman glass microfiber filters GF/C (pore size 1.2 m) (Grasshoff et al. 1999). Water pH was measured using a digital pH meter (pH, 211 Hanna instruments, U.S.A). Electrical conductivity (EC, mS.cm-1) were measured by Coductometer (YSI Model 35 yellow spring, OH, USA).
…show more content…
For this analysis, each environmental variable was firstly analyzed separately (excluding the other variables) in the marginal test, for testing the probable relationship with the data of multivariate community. The variables were then exposed to a forward selection process (sequential test, R2 selection criterion), where, the variability amount described by each variable added to the model is conditional on the variables previously in the model. The P values for the marginal tests were obtained by using 9999 permutations of the non-normalized and transformed data. Then, the sequential tests were done using 9999 permutations of residuals under the reduced model (Anderson 2001). In our study, the DistLM analysis was based on Jaccard and taxonomic similarity of diatom species data and data from environmental